The organization of behavior in Down syndrome children with respect to behavioral competence during the preschool period is a little studied phenomenon. Competence will be assessed with laboratory measures that include mother-child free-play, child mastery motivation, problem solving, self control, and mother-child teaching situations. Also, social status and home environments will be assessed. This is believed to be an important area to study because it defines competent cognitive behaviors that are not restricted to the limited domain of intelligence. Also, these behaviors include social interaction with parents. The design of this study was guided by organizational views of development as expressed by Sroufe and Block and Block. Two groups of children will be studied: (1) Down syndrome children and (2)\normal children matched on developmental age with the Down syndrome children. There will be four assessment periods: 12, 18, 24, and 30 months developmental age; children seen at 12, 18, and 24 months will be followed up 6 months (developmental age) later. Our analyses will be directed at determining the organization of competent behavior with respect to relationships among measures, longitudinal relationships within and across measures, and the effects of maternal behavior on child competence. We will focus on differences between the Down syndrome and normal children both with respect to absolute differences on all of our measures, and to the aspects of behavioral organization described above. Finally, we will examine the relationship between larger social contexts and the development of competence in young Down syndrome and normal children.